The invention relates to a process for manufacturing a blood filter adapted to be disposed within a blood vessel of a mammal body. A specific blood filter is also concerned.
Blood filters are already known.
For manufacturing blood filters, elongated legs are typically created, together with at least a head for joining the legs together, locally. The legs typically extend round an axis of the filter and are radially movable with respect to the axis and the head, between a first, radially restricted position and a second, radially expanded position in which the legs are diverging from the axis (located farer therefrom than in the first position, along a portion of their length).
Examples of such blood filters can be found in U.S. Pat. No. 4,688,553 or U.S. Pat. No. 5,344,427.
So, the prior art discloses the following steps for manufacturing a blood filter:
(a) using a wall comprising a biocompatible material, and
(b) for defining the legs of the blood filter, creating through said wall a series of elongated, essentially parallel sections having a first free end and a second opposed end.
An object of the invention is to improve the steps of manufacturing blood filter.
The following objects are especially expected:
reducing the steps of assembling the different portions of the filter (legs, head . . . ),
reducing the risks possibly induced by local, mechanical constraints created during the steps of manufacturing the blood filter,
improving the cohesion between the above-mentioned different portions of the filter,
potentially reducing the costs for manufacturing the filter,
using possible synergies between the blood filters and the stents or stent grafts.
To that aim, an important feature of the invention recommends to make use of the following steps of manufacturing:
(c) in at least some of the wall sections materialized during the above-mentioned step (b), adjacent, essentially parallel strips (having a non circular transversal section) are created, said strips comprising at least a first strip and a second strip separated by a slot, the strips extending essentially parallel the axis and the slots interrupting at a distance from the first free end of the corresponding wall sections, so that the first strips are integral with the second strips at said first free end, while the second strips are freely movable from the first strips all along the slots (and especially at the second end of the wall sections),
(d) and the first strips are connected therebetween, at the second end.
Even if reducing the mechanical constraints within the blood filter as manufactured is an important object, the invention preferably recommends a further step of angularly shifting the second strips with respect to the first strips, so that in the second position, the first strips are angulated with respect to the axis of the blood filter, while the second strips extend substantially parallel the axis.
It is to be noted that such an  less than  less than angular shifting greater than  greater than  is typically comprised between 30xc2x0 and 40xc2x0, what induces less mechanical constraints in the blood filter than folding back sections of a metallic wire for forming an air pin, as disclosed in U.S. Pat. Nos. 4,688,553, 5,344,427 or 5,383,887.
Further, welding a wire and a metallic plate as in FR-A-2 764 503 is avoided.
For angularly shifting the corresponding strips, the strips can be mechanically moved or a thermal treatment together with a shape-memory material, such as a super-elastic metallic alloy (NiTi) can be used for shifting said strips and for having the first strips moved between the first and second positions.
For improving the reliability of the filter while limiting the costs of manufacturing, it is further recommended, during the step (a), to use an essentially tubular wall and, during step (b), to connect all the first strips one to the others by using a connecting element to which every first strip is fixed, at said second end, the first strips being regularly disposed round the axis.
With reference to the blood filter, the following distinctive features are to be noted: the wall sections  less than  less than cut greater than  greater than  in the original wall individually have the shape of a plate (showing a non circular section) and comprise at least two strips separated by a slot which is interrupted at a distance from the first end, so that the first strips are integral with the second strips at said first end, so that said firststrips define the legs of the blood filter and the second strips define centering elements for centering the blood filter within the blood vessel.